Improvement in switches for district-telephone systems



3 Sheets-#Sheet 1 v T.4B. DOOLITTLE.. v Y Switch for District TelephoneSystem. ANo. 209,115. v Y Patented Oct. 22, 1878.

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. T. B. DOOLITTLE.A

Switch for District Telephone System. No. 209,115. Patented Oct.22,1878.

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T. B. DOOLI'TTLB. Switch for District Telephone System.. No. 209,115.Patented Oct. `22,- 1878.

UNITED STATES PATE-NTOFFICE.l

THOMAS B. :oOoLI-TTLE, OF BRIDGEPORT, CONNECTICUT.

IMPROVMENT IN SWITCl-lES FOR DISTRICT-TELEPHONE SYSTEMS.

Speciiication forming part of Letters Patent No. 209,115, dated October22, 1878; application filed April 10, 1878,.

To all/wm it may concern:

Be it known that I, THOMAS B. DO'OLITTLE, of Bridgeport, in the countyof Fairfield and State of Connecticut, have invented certain new anduseful Improvements in District-Telephone Systems; and l do herebydeclare that the following is a full and exact description thereof,reference being had to the accompanying drawings, makin g-a part of thisspeciication.

My invention relates to certain improvements in the art of transmittingsound and messages by the use of the telephone.

It has for its object to render sound or mes; sages sent through a wirebetween given points inaudible at any other than the initial andobjective points; and consists not only of a general system, somewhatsimilarto the American District Telegraph, involving' a main ofce, wirecircuits, battery, and a code of signals, but also of a novel instrumentarranged in connection with the telephones along the line, whereby thetelephones on any given circuit or circuits may bc switched together andmessages transmitted between any two, all the balance being cut ont andprevented from taking up the message or conversation, as will behereinafter more fully explained.

In the use of the telephone system as it exists at present, where morethan two stations are connected with a line-wire, there is no practicalmeans, that I am aware of, of preventing a message between any twostations from being heard or picked up at any or all ofthe otherstations. This condition of things is a great disadvantage in the use ofthe telephone in a district system, where notice is sent to a mainoffice to respond to an inquiry, or a command given to put two stationsin communication.

My invention overcomes these disadvan-v ties so separated willv inducethe third party to cease the use of his telephone, such cessationautomatically re-establishing the conditions previously existing'.

To embody this system in practical form the following condition ofthings must exist:

There must be a central or main office, connected with the outlyingstations by a circuit or circuits of wire. The circuit-wires enteringthe line, while at the same time the wire is cnt out behind any suchstation. This instrument will be described in detail presently.

In order that my general system and the novel devices employed may befully understood, I will proceed to describe thesame, referring byletters to the accompanying drawings, in which- Figure l represents thearrangement ot wires and devices in the main office, including anovelswitch-board, an annunciator, system of bells, series of batteries,and one or more telephones. Fi g. 2 is view, partially in elevation andpartly in section, of a novel instrument which I use at each station inconnection with the telephones. Fig. 3 is a plan, illustrating thegeneral system in operation and the results accomplished; and Fig. 4 isa plan view of the end of the instrument illustrated at Fig. 2, showinga detail of construction hereinafter referred to.

Vhere the same parts appear in the several gures they are designated bythe same letters. I will rst in order refer particularly to Fig.

V1, in which 1 2 3 4, te., are a series of wires or lines entering themain oftice. These wires have connected with each a bell, A, and enteran annunciator, B, provided with drop-signs,

which are operated by the current passingthrough the wires or lines towhich they are respectively connected from this annunciator B. The linesl 2 3, Ste., connect with a switchboard, C, to which are also attachedone or more telephones.

D D, Sac., are vertical parallel metal bars, and E E, Sto.,switch-cranks, by which the connections and changes inthe circuits aremade.

F F represent two telephones, which, by reason of their connection withthe switchboard, may be'put on any circuit or line. I preferably usetwo, in order that the use of any given circuit by subscribers may notprevent the receipt of signals or messages through any other independentline.

G G, &c., are a series of batteries, connected with the series of wires1 2 3, &c., by any suitablemeans andH H, te., are aseries ot'pushbuttons,7 for giving signals to given stations by making andbreaking the circuit.

I have shown the closed-circuit system, but, of course, do not coninemyself in this respect. The metal bars and switch-cranks on theswitchboard are, as before described, arranged parallel. The cranks arepivoted at their upper ends, the objects of this arrangement being thatthe attendant of the switch-board can, at

a glance, determine whether the circuits are in their normal conditionor whether they have been changed, as the eye will readily detect anycrank out of' a vertical line, and draw attenion to the fact that acircuit has been create The advantage of pivoting the cranks at theirupper ends relative to their movement is that any tendency to gravitate,should they become loose, will not tend to accidentally establish anundesired circuit, which might be the case were the cranks pivotedbelow.

I will now proceed to `describe Fig. 2. I is a box or case, of anydesirable form and material, upon which is arranged an alarm-bell, J,and armature K.

L is a bell-hammer, pivoted to the box or case, and operated by thecurrent passing through the line-wire l.

F is a telephone, connected by wires to the posts M M on the case, cbeing a line and cl a ground wire.

N and N are two metal screw rods or bars, passing horizontally throughthe case in any convenient manner, and connected together by a wire, e,which vwire or another connects the rod N with the telephone line-wirepost M.

O and Oare two more cross-rods, similar to those just described, andarranged below and parallel with the same; and P is a metal walking beamor bar, suitably notched, and resting horizontally upon the rods O O',in which position it is held against accidental displacement, and towhich position it is antomatically returned, it' moved, by a spiralspring, Q, arranged as shown, one end to the bar P and the otherconnected to the case.

B. is a bow-spring, secured at the center to the bar P, and out ofcontact with the rods N `N' when in normal position. The object of thisspringis to keep bright and free from dirt the under sides of the rods NN and the top surface of the bar P, which is accomplished by thelongitudinal movement of the ends of the spring when the bar P isvibrated, and the presence of any matter which might effect conductivityis avoided.

The line-wire l joins the bell-hammer post to the lower cross-rod, O,and the other end of the line-wire comes into the box from the oppositeside and connects with the other lower cross-rod, 0', so that when thebar P is in its normal position on the rods O O it completes the line.

Instead of the two posts N N and wire e, I may, of course, use a singlebar or plate.

From this construction and arrangement it will be seen that when theparts are in the position described the line-wire l is completed, orcontinued through the box or case by the bar P and its contact with thecross-rods O O', and that the telephone is in no manner connected withthe line, but may be connected therewith in either direction bydepressing one or the other end ofthe bar P, the ends of which projectthrough the end of the box or case, and, when desired, may be soconstructed that the bar cannot be weighted down, and thus guard againstcontinued depression of the lever beyond the time absolutely necessary.

The result of depressing either end of the bar P will be manifest byobserving the dotted lines, which show the bar with its left enddepressed. 'Ihe right end has been elevated and has left contact withthe. cross-rod O', and completely 4broken the connection with theline-wire to the right of the box as etectually as it' it hadoriginallyte1minated at the box, while it has, by reason of coming incontact with the cross-bar N,.esta blished communication between theline-wire 1,\to the left'of the box, and the cross-bar N', which,through the medium of the wire e, cross-rod N, post M, and

wire c, has brought the telephone F onto the'm line. rIhe bow-spring R,it may here be remarked, not only subserves the ends before4 referredto, but also tends to maintain contact, which might otherwise beunintentionally broken by any slight tremulous movement of the end ofthe lever P.

When the end of the bar P is released, the spiral spring Q, returns thebar to its .normal position on the cross-bars O O' and cuts out thetelephone F, so that all the telephones can only be put on the line byamechanical movement and operation. The end ot' the bar P must be keptdepressed so long as the telcphone is in use; but to prevent it frombeing y so held beyond the time required by any forgetfulness, I proposeto either curve the ends of the bar P, so that they cannot be weighteddown, or when it is desiredto provide a special means to hold it down tofree the hands, I employ such means as I have illustrated at Fig. 4 ofthe drawings, which consists of a hook,

f, upon which to hang the telephone when not in use, such hook beingarranged under the end ot' bar P, so that when it is depressed andcaught by a latch, g, the hook j' is covered or concealed, and itfollows that before the telew W l-"W phone can be hung in place afteruse the latch g must be released, whereupon the spiral spring Q in thebox immediately returns the bar P to its position, cutting out thetelephone and re-establishing the main line. Were the bar P vibrated inthe opposite direction to that shown in dotted lines at Fig. 2, thecross-rods 0 and N would be brought in connection, and, a priori, theline-wire l cut out from the left of the box or case.

Now, having described Figs. 1, 2, and 4, I will now, by reference toFig. 3, illustrate how any station or subscriber can signal andcommunicate with the main office, and be put in connection orcommunication with any other station or subscriber on the same or anyother circuit, and converse with said station without bein-g heard atany other point on the line.

Let S represent the main office, and suppose stations 2 3 4 5 are on asingle limewire to the left of the ofiice, at each of which stationsthere are telephones, between which and the line-wire are arranged thedevices shown at Fig. 2 of the drawings. In the iigure I am nowreferring to I have only shown so much of the device as is necessary toillustrate the operation of cutting in and out. Now, a person at stationNo. 5 desirin gto converse conlidentially with a party at station No. 3first depresses the right-hand end ofbar P. This act produces atemporary break in the circuit and rings the alarm-bell at main oftlce,and drops the sign in the annunciator corresponding to the circuitsending the signal. The attendant immediately puts his telephone incircuit by means of theswitch, and person at station No. 5 informs himthat he desires to speak with the party at station No. 3. The attendantthen, by means ofthe push-button between the battery and such line,gives No. 3 the signal appropriated to. that station, and then by thetelephone informs him that No. 5 wishes to talk to him. No.3 thendepresses the left end of lever or bar P at his station, breaks the linebetween said station andmain office, and puts -ation No. 3 in telephoniecommunication with It will be observed that at all intermediate stationsthe telephones are normally out of thecircuit. When No. 5 and No.3 ceaseconversation the bars P are released, and vboth telephones areautomatically cut out and the original circuit-line re-established.

If, during the time No.5 and No.3 are using the line, station No.2should wish to converse with 4main oflice or any station on any otherline-say, station No. 2 on line-wire No. 6-the main office would benotied, and by the observance of the steps just described No. 2 onlinewire No. land No.2 online No.6 could converse at same time Nos. 3and 5 were in communication. Now, suppose that while No. 5 and No. 3 areconversing No.4 should attempt to get in on the line, either for thepurpose of calling main office or for picking up conversation 'betweenNo. 5 and No. 3, the necessary movement of the lever-bar P to put him onthe line with the office would only put him on line with No. 3, and atthe same time cut out No. 5, which No. 3 would, of course, know 5 or, ifNo. 4 should reverse the movement of the bar P, he would be incommunication with No. 5, and No. 3 cutv out, and the same result wouldensue, and the moment he leaves his telephone the self-actin g bar Pre-establishes the line between N o. 5 and No. 3.

Of course many changes may be made in the details of construction andarrangement of the devices employed without departing from the spirit ofmy invention; but

What I claim as new, and desire to secure by Letters Patent, is

l. In a district-telephone system, a series of switches, normallyconstituting portions of the main line, and adapted to sever the mainline and complete a circuit from the .earth at any station througheither fragment of the brok'en main line on either side of said station,sub stantially as and for the purposes specified.

2. A district-telephone switch of conducting material, normally forminga portion of the main line and resting on two conductingposts of mainline, and adapted to be swung about either of said posts, as centers,into contact with a metallic 'post having a groundconnection,substantially as hereinbefore set forth.

3. The case I, provided with an alarm-bell and armature, a vibratorybar, and four cross-rods and wire connections,substantially as and forthe 'purposes set forth.

4. In combination with the vibratory bar P and the cross-bars N N', thebow-spring It, substantially as and for the purposes set forth.

5. The lever ends of the bar P, formed as described, in combination withthe suspension-hook f and latch g, arranged to operate iff/wb

